Process of dyeing organic cellulose esters



Patented Oct. 13, 1931 UNITED STATES PATENT OFFICE WINFRID HENTRICH. 0F WIESbORF-ON-THE-RHINE, GERMANY, ASSIGNOR TO GENERAL ANILINE WORKS, INC., OF NEW YORK, N. Y., A CORPORATION OF DELAWARE PROCESS OF DYEING ORGANIC CELLULOSE ESTERS No Drawing. Original application filed February 4, 1927, Serial No. 166,013. Patent No. 1,695,654, and

in Germany February 26, 1926. Divided and this application filed 0ct0ber-18, 1927. Serial No.

I have invented new and useful improvements in processes of dyeing organic cellulose esters.

' My invention consists in the use of certain classes of azo dyestuffs for the dyeing of organic cellulose ester products such as cellulose formate, cellulose acetate, etc.

Whereas only very few mono azo dyestufis show any afiinity for organic cellulose esters, I have found that the products which are obtained by coupling diazo compounds of dinitro amino phenols or their derivatives with unsulfonated and non-carboxylated amino-naphthols in the presence of an agent capable of binding mineral acids such as sodium carbonate and sodium acetate, dye readily cellulose esters. The dyes so ob- .tained dye brownish-red,brown, and violet are characterized by to black shades which their remarkable fastness' properties, especially their fastness to washing and wetting. It is of especial importance that now for the first time, by the use of certain of these dyes, acetate silk may be dyed deep black colors directly by means of water-soluble dyestuffs from a neutral or slightly-acid bath, i. e.. a non-alkalinebath. Bydiazotizing and developing the dyes uponthe fibers the shades are deepened and the fastness properties,

especiallythe overcolor and light fastness properties, are improved.

In order to illustrate further my invention, the following example is given, it being understood that the invention is not confined to this example:

E mample 5 parts of the dyestufi' prepared by coupling diazotized 4.6-dinItro-2-aminol-hyclroxy-benzol with 1-amino-8-hydroxynaphthalenem the presence of sodium carbonate, said dyestufi' having the following formula:

one) om N=Nomm New are dissolved in 3000 parts of hot water. 100 parts of cellulose acetate threads are entered into the hot dye bath and kept therein for about 7 hour at 7 0 C. The skeins are squeezed out, rinsed and dried in' the usual way. Deep black shades of excellent fastness properties are obtained.

This application is a division of my U. S. Patent 1,695,654, dated December 18, 1928, (application filed February 4, 1927,. Serial No. 166,013). i

I claim:

1. Process for dyeing cellulose esters which comprises contacting the same with a nonalkaline aqueous solution of a dyestufl' substantially identical with a dyestufi' obtainable by coupling the diazo-compound of a dinitroamino phenol with an unsulfonated and noncarboxylated amino naphthol in the presence of an agent capable of binding mineral acids.

2. Process for dyeing cellulose esters which comprises contacting the same with a nonalkaline aqueous solution of a dyestuff having most probably the formula:

OII(8) 3. Process for dyeing cellulose esters which my hand.

VVINFRID HENTRICH. 

